The fourth
edition of the Diagnostic and Statistical Manual of Mental
Disorders (DSM-IV) lists four major categories of
insomnia whereas the International Classification of Sleep
Disorders (ICSD)comprises approximately 40 categories
having insomnia as the prominent complaint. In the ICSD,
insomnia is included within the category of dyssomnia and can
occur with extrinsic, intrinsic, and circadian rhythm sleep
disorders